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</head><body><div id="web_bg"></div><div id="sidebar"><div id="menu-mask"></div><div id="sidebar-menus"><div class="author-avatar"><img class="avatar-img" data-lazy-src="https://qiniu.codekylin.cn/img/20200807181526.jpg" onerror="onerror=null;src='https://qiniu.codekylin.cn/github/img/friend_404.gif'" alt="avatar"/></div><div class="site-data"><div class="data-item is-center"><div class="data-item-link"><a href="/archives/"><div class="headline">文章</div><div class="length-num">362</div></a></div></div><div class="data-item is-center"><div class="data-item-link"><a href="/tags/"><div class="headline">标签</div><div class="length-num">427</div></a></div></div><div class="data-item is-center"><div class="data-item-link"><a href="/categories/"><div class="headline">分类</div><div class="length-num">101</div></a></div></div></div><hr/><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fa fa-home"></i><span> 首页</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fa fa-archive"></i><span> 时间轴</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fa fa-tags"></i><span> 标签</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fa fa-folder-open"></i><span> 分类</span></a></div><div class="menus_item"><a class="site-page" href="/link/"><i class="fa-fw fa fa-link"></i><span> 友链</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fa fa-heart"></i><span> 关于</span></a></div></div></div></div><div class="post" id="body-wrap"><header class="post-bg" id="page-header" style="background-image: url('https://qiniu.codekylin.cn/github/img/img/wallhaven-4xlkjz.jpg')"><nav id="nav"><span id="blog_name"><a id="site-name" href="/">Kylin</a></span><div id="menus"><div id="search-button"><a class="site-page social-icon search"><i class="fas fa-search fa-fw"></i><span> 搜索</span></a></div><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fa fa-home"></i><span> 首页</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fa fa-archive"></i><span> 时间轴</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fa fa-tags"></i><span> 标签</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fa fa-folder-open"></i><span> 分类</span></a></div><div class="menus_item"><a class="site-page" href="/link/"><i class="fa-fw fa fa-link"></i><span> 友链</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fa fa-heart"></i><span> 关于</span></a></div></div><div id="toggle-menu"><a class="site-page"><i class="fas fa-bars fa-fw"></i></a></div></div></nav><div id="post-info"><h1 class="post-title">Java之函数式接口</h1><div id="post-meta"><div class="meta-firstline"><span class="post-meta-date"><i class="far fa-calendar-alt fa-fw post-meta-icon"></i><span class="post-meta-label">发表于</span><time class="post-meta-date-created" datetime="2020-09-23T08:46:30.000Z" title="发表于 2020-09-23 16:46:30">2020-09-23</time><span class="post-meta-separator">|</span><i class="fas fa-history fa-fw post-meta-icon"></i><span class="post-meta-label">更新于</span><time class="post-meta-date-updated" datetime="2022-07-12T11:42:50.034Z" title="更新于 2022-07-12 19:42:50">2022-07-12</time></span><span class="post-meta-categories"><span class="post-meta-separator">|</span><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/Java/">Java</a><i class="fas fa-angle-right post-meta-separator"></i><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/Java/Java8/">Java8</a></span></div><div class="meta-secondline"><span class="post-meta-separator">|</span><span class="post-meta-wordcount"><i class="far fa-file-word fa-fw post-meta-icon"></i><span class="post-meta-label">字数总计:</span><span class="word-count">2.1k</span><span class="post-meta-separator">|</span><i class="far fa-clock fa-fw post-meta-icon"></i><span class="post-meta-label">阅读时长:</span><span>8分钟</span></span></div></div></div></header><main class="layout" id="content-inner"><div id="post"><article class="post-content" id="article-container"><h2 id="函数式接口"><a href="#函数式接口" class="headerlink" title="函数式接口"></a>函数式接口</h2><p><strong><mark>只包含一个抽象方法的接口，称为函数式接口。</mark></strong></p>
<p>你可以通过 Lambda 表达式来创建该接口的对象。(若 Lambda 表达式抛出一个受检异常(即:非运行时异常)，那么该异常需要在目标接口的抽象方法上进行声明)。</p>
<p>我们可以在一个接口上使用 <code>@FunctionalInterface</code>注解，这样做可以检查它是否是一个函数式接口。同时 javadoc 也会包含一条声明，说明这个接口是一个函数式接口。</p>
<p>在<code>java.util.function</code>包下定义了Java 8 的丰富的函数式接口</p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923165331.png" alt="image-20200923165329350"></p>
<p>我们查看<code>Comparator</code>接口源码。发现了一些矛盾的地方。</p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923165758.png" alt="image-20200923165757180"></p>
<p>我们发现了该接口中不止包含了一个方法，还存在大量的<code>default</code>和<code>static</code>方法。这和上文的定义是矛盾的！！</p>
<p><strong>在jdk8之前，interface之中可以定义变量和方法，变量必须是public、static、final的，方法必须是public、abstract的。由于这些修饰符都是默认的，JDK8及以后，允许我们在接口中定义static方法和default方法。</strong></p>
<p> <mark><strong>JDK8接口中的静态方法和默认方法，都不算是抽象方法。。接口默认继承java.lang.Object，所以如果接口显示声明覆盖了Object中方法，那么也不算抽象方法。</strong></mark></p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923170230.png" alt="image-20200923170228916"></p>
<p>所以该接口的确是一个函数式接口！！</p>
<p>Java从诞生日起就是一直倡导“一切皆对象”，在Java里面面向对象(OOP) 编程是一切。但是随着python、scala等语言的兴起和新技术的挑战，Java不 得不做出调整以便支持更加广泛的技术要求，也即java不但可以支持OOP还 可以支持OOF(面向函数编程)</p>
<p>在函数式编程语言当中，函数被当做一等公民对待。在将函数作为一等公民的 编程语言中，Lambda表达式的类型是函数。但是在Java8中，有所不同。在 Java8中，Lambda表达式是对象，而不是函数，它们必须依附于一类特别的 对象类型——函数式接口。</p>
<p>简单的说，在Java8中，Lambda表达式就是一个函数式接口的实例。这就是 Lambda表达式和函数式接口的关系。也就是说，只要一个对象是函数式接口 的实例，那么该对象就可以用Lambda表达式来表示。</p>
<p>所以以前用匿名实现类表示的现在都可以用Lambda表达式来写。</p>
<h2 id="FunctionalInterface"><a href="#FunctionalInterface" class="headerlink" title="@FunctionalInterface"></a><strong>@</strong>FunctionalInterface</h2><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923170603.png" alt="image-20200923170602530"></p>
<ol>
<li><p>该注解只能标记在”有且仅有一个抽象方法”的接口上。</p>
</li>
<li><p>JDK8接口中的静态方法和默认方法，都不算是抽象方法。</p>
</li>
<li><p>接口默认继承java.lang.Object，所以如果接口显示声明覆盖了Object中方法，那么也不算抽象方法。</p>
</li>
<li><p>该注解不是必须的，如果一个接口符合”函数式接口”定义，那么加不加该注解都没有影响。加上该注解能够更好地让编译器进行检查。如果编写的不是函数式接口，但是加上了@FunctionInterface，那么编译器会报错。</p>
</li>
</ol>
<h2 id="自定义函数式接口"><a href="#自定义函数式接口" class="headerlink" title="自定义函数式接口"></a>自定义函数式接口</h2><p>通过对函数式接口概念的认知，我们现在来自定义一个<code>MyFunctionInterface</code> 函数式接口测试。</p>
<h3 id="只包含一个抽象方法"><a href="#只包含一个抽象方法" class="headerlink" title="只包含一个抽象方法"></a>只包含一个抽象方法</h3><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923171415.png" alt="image-20200923171412859"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//自定义函数式接口</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">MyFunctionInterface</span>&lt;<span class="title">T</span>&gt; </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//抽象方法</span></span><br><span class="line">    <span class="function">T <span class="title">test</span><span class="params">(T t)</span></span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p>测试类<code>TestFunction</code></p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923171515.png" alt="image-20200923171514395"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">TestFunction</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>&#123;</span><br><span class="line">        MyFunctionInterface&lt;String&gt; function = (str) -&gt; &#123;</span><br><span class="line">            <span class="keyword">return</span> str;</span><br><span class="line">        &#125;;</span><br><span class="line"></span><br><span class="line">        System.out.println(function.test(<span class="string">&quot;FunctionInterface Test！&quot;</span>));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h3 id="包含一个覆盖Object方法"><a href="#包含一个覆盖Object方法" class="headerlink" title="包含一个覆盖Object方法"></a>包含一个覆盖Object方法</h3><p>覆盖Object的 <code>hashCode</code>方法</p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923171730.png" alt="image-20200923171729178"></p>
<p>再次运行测试类，成功！说明它是一个函数式接口</p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923171840.png" alt="image-20200923171514395"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//自定义函数式接口</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">MyFunctionInterface</span>&lt;<span class="title">T</span>&gt; </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//抽象方法</span></span><br><span class="line">    <span class="function">T <span class="title">test</span><span class="params">(T t)</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//覆盖Object方法</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">hashCode</span><span class="params">()</span></span>;</span><br><span class="line">    </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h3 id="包含一个default方法"><a href="#包含一个default方法" class="headerlink" title="包含一个default方法"></a>包含一个default方法</h3><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923172019.png" alt="image-20200923172018308"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//自定义函数式接口</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">MyFunctionInterface</span>&lt;<span class="title">T</span>&gt; </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//抽象方法</span></span><br><span class="line">    <span class="function">T <span class="title">test</span><span class="params">(T t)</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//覆盖Object方法</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">hashCode</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//默认方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">default</span> <span class="keyword">void</span> <span class="title">defaultMethod</span><span class="params">()</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p>再次运行测试类，成功！说明它default不是抽象方法，该接口是一个函数式接口</p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923171840.png" alt="image-20200923171514395"></p>
<h3 id="包含一个static方法"><a href="#包含一个static方法" class="headerlink" title="包含一个static方法"></a>包含一个static方法</h3><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923185339.png" alt="image-20200923185337449"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">MyFunctionInterface</span>&lt;<span class="title">T</span>&gt; </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//抽象方法</span></span><br><span class="line">    <span class="function">T <span class="title">test</span><span class="params">(T t)</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//覆盖Object方法</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">hashCode</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//默认方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">default</span> <span class="keyword">void</span> <span class="title">defaultMethod</span><span class="params">()</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//静态方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">staticMethod</span><span class="params">()</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p>再次运行测试类，成功！说明它static不是抽象方法，该接口是一个函数式接口</p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923171840.png" alt="image-20200923171514395"></p>
<h3 id="标注-FunctionInterface注解"><a href="#标注-FunctionInterface注解" class="headerlink" title="标注@FunctionInterface注解"></a>标注@FunctionInterface注解</h3><p>通过前面的测试，我们可以明确知道，只要该接口只含有一个抽象方法，它就是一个函数式接口。而不是一定要标注@FunctionInterface注解，这两者之间没有绝对的联系。</p>
<p><strong>该注解不是必须的，如果一个接口符合”函数式接口”定义，那么加不加该注解都没有影响。加上该注解能够更好地让编译器进行检查。如果编写的不是函数式接口，但是加上了@FunctionInterface，那么编译器会报错。</strong></p>
<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923185745.png" alt="image-20200923185744315"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//自定义函数式接口</span></span><br><span class="line"><span class="meta">@FunctionalInterface</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">MyFunctionInterface</span>&lt;<span class="title">T</span>&gt; </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//抽象方法</span></span><br><span class="line">    <span class="function">T <span class="title">test</span><span class="params">(T t)</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//覆盖Object方法</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">hashCode</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//默认方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">default</span> <span class="keyword">void</span> <span class="title">defaultMethod</span><span class="params">()</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">//静态方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">staticMethod</span><span class="params">()</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h2 id="四大核心函数式接口"><a href="#四大核心函数式接口" class="headerlink" title="四大核心函数式接口"></a>四大核心函数式接口</h2><table>
<thead>
<tr>
<th align="center">函数式接口</th>
<th>参数类型</th>
<th>返回类型</th>
<th>用途</th>
</tr>
</thead>
<tbody><tr>
<td align="center"><code>Consumer&lt;T&gt;</code>消费型</td>
<td>T</td>
<td>void</td>
<td>对类型为T的对象应用操作，包含方法：<code>void accept(T t)</code></td>
</tr>
<tr>
<td align="center"><code>Supplier&lt;T&gt;</code>供给型</td>
<td>无</td>
<td>T</td>
<td>对类型为T的对象，包含方法：<code>T get()</code></td>
</tr>
<tr>
<td align="center"><code>Function&lt;T,R&gt;</code>函数型</td>
<td>T</td>
<td>R</td>
<td>对类型为T的对象应用操作，并返回结果。结果是R类型的对象。包含方法：<code>R apply(T t)</code></td>
</tr>
<tr>
<td align="center"><code>Predicate&lt;T&gt;</code>断定型</td>
<td>T</td>
<td>boolean</td>
<td>确定类型为T的对象是否满足某约束，并返回boolean值。包含方法<code>boolean test(T t)</code></td>
</tr>
</tbody></table>
<h3 id="Consumer消费型"><a href="#Consumer消费型" class="headerlink" title="Consumer消费型"></a>Consumer消费型</h3><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923194006.png" alt="image-20200923193957077"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test1</span><span class="params">()</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    happyTime(<span class="number">500</span>, <span class="keyword">new</span> Consumer&lt;Double&gt;() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">accept</span><span class="params">(Double aDouble)</span> </span>&#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;学习太累了，去天上人间买了瓶矿泉水，价格为：&quot;</span> + aDouble);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line"></span><br><span class="line">    System.out.println(<span class="string">&quot;********************&quot;</span>);</span><br><span class="line"></span><br><span class="line">    happyTime(<span class="number">400</span>,money -&gt; System.out.println(<span class="string">&quot;学习太累了，去天上人间喝了口水，价格为：&quot;</span> + money));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">happyTime</span><span class="params">(<span class="keyword">double</span> money, Consumer&lt;Double&gt; con)</span></span>&#123;</span><br><span class="line">    con.accept(money);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923192402.png" alt="image-20200923192400600"></p>
<h3 id="Supplier供给型"><a href="#Supplier供给型" class="headerlink" title="Supplier供给型"></a>Supplier供给型</h3><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923193155.png" alt="image-20200923193152964"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test2</span><span class="params">()</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">    System.out.println(get(<span class="keyword">new</span> Supplier&lt;String&gt;() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> String <span class="title">get</span><span class="params">()</span> </span>&#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="string">&quot;犯罪人：张三&quot;</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;));</span><br><span class="line"></span><br><span class="line">    System.out.println(get(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="string">&quot;法外狂徒三哥！&quot;</span>;</span><br><span class="line">    &#125;));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">get</span><span class="params">(Supplier&lt;String&gt; supplier)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">return</span> supplier.get();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923193222.png" alt="image-20200923193220508"></p>
<h3 id="Function函数型接口"><a href="#Function函数型接口" class="headerlink" title="Function函数型接口"></a>Function函数型接口</h3><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923193914.png" alt="image-20200923193912896"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test3</span><span class="params">()</span> </span>&#123;</span><br><span class="line">    System.out.println(getLength(<span class="string">&quot;test&quot;</span>, <span class="keyword">new</span> Function&lt;String, Integer&gt;() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> Integer <span class="title">apply</span><span class="params">(String s)</span> </span>&#123;</span><br><span class="line">            <span class="keyword">return</span> s.length();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;));</span><br><span class="line"></span><br><span class="line">    System.out.println(getLength(<span class="string">&quot;lambda&quot;</span>, str -&gt; str.length()));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getLength</span><span class="params">(String s, Function&lt;String, Integer&gt; function)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">return</span> function.apply(s);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923194005.png" alt="image-20200923192317870"></p>
<h3 id="Predicate断定型接口"><a href="#Predicate断定型接口" class="headerlink" title="Predicate断定型接口"></a>Predicate断定型接口</h3><p><img src= "https://gitee.com/kylincw/images/raw/master/loading.gif" data-lazy-src="https://qiniu.codekylin.cn/img/20200923194233.png" alt="image-20200923194231733"></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test4</span><span class="params">()</span> </span>&#123;</span><br><span class="line">    List&lt;String&gt; list = Arrays.asList(<span class="string">&quot;北京&quot;</span>, <span class="string">&quot;南京&quot;</span>, <span class="string">&quot;天津&quot;</span>, <span class="string">&quot;东京&quot;</span>, <span class="string">&quot;西京&quot;</span>, <span class="string">&quot;普京&quot;</span>);</span><br><span class="line"></span><br><span class="line">    List&lt;String&gt; filterStrs = filterString(list, <span class="keyword">new</span> Predicate&lt;String&gt;() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">test</span><span class="params">(String s)</span> </span>&#123;</span><br><span class="line">            <span class="keyword">return</span> s.contains(<span class="string">&quot;津&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line"></span><br><span class="line">    System.out.println(filterStrs);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">    List&lt;String&gt; filterStrs1 = filterString(list, s -&gt; s.contains(<span class="string">&quot;京&quot;</span>));</span><br><span class="line">    System.out.println(filterStrs1);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">//根据给定的规则，过滤集合中的字符串。此规则由Predicate的方法决定</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> List&lt;String&gt; <span class="title">filterString</span><span class="params">(List&lt;String&gt; list, Predicate&lt;String&gt; pre)</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">    ArrayList&lt;String&gt; filterList = <span class="keyword">new</span> ArrayList&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">for</span> (String s : list) &#123;</span><br><span class="line">        <span class="keyword">if</span> (pre.test(s)) &#123;</span><br><span class="line">            filterList.add(s);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> filterList;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

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<h2 id="其他接口"><a href="#其他接口" class="headerlink" title="其他接口"></a>其他接口</h2><table>
<thead>
<tr>
<th>函数式接口</th>
<th>参数类型</th>
<th>返回类型</th>
<th>用途</th>
</tr>
</thead>
<tbody><tr>
<td>BiFunction&lt;T, U, R&gt;</td>
<td>T, U</td>
<td>R</td>
<td>对类型为 T, U 参数应用操作，返回 R 类型的结 果。包含方法为: R apply(T t, U u);</td>
</tr>
<tr>
<td>UnaryOperator<T> (Function子接口)</td>
<td>T</td>
<td>T</td>
<td>对类型为T的对象进行一元运算，并返回T类型的 结果。包含方法为:T apply(T t);</td>
</tr>
<tr>
<td>BinaryOperator<T> (BiFunction 子接口)</td>
<td>T, T</td>
<td>T</td>
<td>对类型为T的对象进行二元运算，并返回T类型的 结果。包含方法为: T apply(T t1, T t2);</td>
</tr>
<tr>
<td>BiConsumer&lt;T, U&gt;</td>
<td>T, U</td>
<td>void</td>
<td>对类型为T, U 参数应用操作。 包含方法为: void accept(T t, U u)</td>
</tr>
<tr>
<td>BiPredicate&lt;T,U&gt;</td>
<td>T,U</td>
<td>boolean</td>
<td>包含方法为: boolean test(T t,U u)</td>
</tr>
<tr>
<td>ToIntFunction&lt; T &gt; ToLongFunction&lt; T &gt; ToDoubleFunction&lt; T &gt;</td>
<td>T</td>
<td>int long double</td>
<td>分别计算int、long、double值的函数</td>
</tr>
<tr>
<td>IntFunction&lt; R &gt; LongFunction&lt; R &gt; DoubleFunction&lt; R &gt;</td>
<td>int long double</td>
<td>R</td>
<td>参数分别为int、long、double 类型的函数</td>
</tr>
</tbody></table>
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</article><div class="post-copyright"><div class="post-copyright__author"><span class="post-copyright-meta">文章作者: </span><span class="post-copyright-info"><a href="mailto:undefined">Kylin</a></span></div><div class="post-copyright__type"><span class="post-copyright-meta">文章链接: </span><span class="post-copyright-info"><a href="https://www.codekylin.cn/63744.html">https://www.codekylin.cn/63744.html</a></span></div><div class="post-copyright__notice"><span class="post-copyright-meta">版权声明: </span><span class="post-copyright-info">本博客所有文章除特别声明外，均采用 <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" target="_blank">CC BY-NC-SA 4.0</a> 许可协议。转载请注明来自 <a href="https://www.codekylin.cn" target="_blank">Kylin</a>！</span></div></div><div class="tag_share"><div class="post-meta__tag-list"><a class="post-meta__tags" href="/tags/java/">java</a><a class="post-meta__tags" href="/tags/%E5%87%BD%E6%95%B0%E5%BC%8F%E6%8E%A5%E5%8F%A3/">函数式接口</a></div><div class="post_share"><div 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class="toc-item toc-level-2"><a class="toc-link" href="#FunctionalInterface"><span class="toc-number">2.</span> <span class="toc-text">@FunctionalInterface</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%87%AA%E5%AE%9A%E4%B9%89%E5%87%BD%E6%95%B0%E5%BC%8F%E6%8E%A5%E5%8F%A3"><span class="toc-number">3.</span> <span class="toc-text">自定义函数式接口</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%8F%AA%E5%8C%85%E5%90%AB%E4%B8%80%E4%B8%AA%E6%8A%BD%E8%B1%A1%E6%96%B9%E6%B3%95"><span class="toc-number">3.1.</span> <span class="toc-text">只包含一个抽象方法</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%8C%85%E5%90%AB%E4%B8%80%E4%B8%AA%E8%A6%86%E7%9B%96Object%E6%96%B9%E6%B3%95"><span class="toc-number">3.2.</span> <span class="toc-text">包含一个覆盖Object方法</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%8C%85%E5%90%AB%E4%B8%80%E4%B8%AAdefault%E6%96%B9%E6%B3%95"><span class="toc-number">3.3.</span> <span class="toc-text">包含一个default方法</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%8C%85%E5%90%AB%E4%B8%80%E4%B8%AAstatic%E6%96%B9%E6%B3%95"><span class="toc-number">3.4.</span> <span class="toc-text">包含一个static方法</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%A0%87%E6%B3%A8-FunctionInterface%E6%B3%A8%E8%A7%A3"><span class="toc-number">3.5.</span> <span class="toc-text">标注@FunctionInterface注解</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E5%9B%9B%E5%A4%A7%E6%A0%B8%E5%BF%83%E5%87%BD%E6%95%B0%E5%BC%8F%E6%8E%A5%E5%8F%A3"><span class="toc-number">4.</span> <span class="toc-text">四大核心函数式接口</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#Consumer%E6%B6%88%E8%B4%B9%E5%9E%8B"><span class="toc-number">4.1.</span> <span class="toc-text">Consumer消费型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#Supplier%E4%BE%9B%E7%BB%99%E5%9E%8B"><span class="toc-number">4.2.</span> <span class="toc-text">Supplier供给型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#Function%E5%87%BD%E6%95%B0%E5%9E%8B%E6%8E%A5%E5%8F%A3"><span class="toc-number">4.3.</span> <span class="toc-text">Function函数型接口</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#Predicate%E6%96%AD%E5%AE%9A%E5%9E%8B%E6%8E%A5%E5%8F%A3"><span class="toc-number">4.4.</span> <span class="toc-text">Predicate断定型接口</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E5%85%B6%E4%BB%96%E6%8E%A5%E5%8F%A3"><span class="toc-number">5.</span> <span class="toc-text">其他接口</span></a></li></ol></div></div><div class="card-widget card-recent-post"><div class="item-headline"><i class="fas fa-history"></i><span>最新文章</span></div><div class="aside-list"><div class="aside-list-item"><a class="thumbnail" href="/56352.html" title="be动词"><img 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